DE3446138A1 - METHOD FOR DETERMINING THE POSITION OF A WORKPIECE IN AN NC-CONTROLLED MACHINE, AND AN NC-CONTROLLED MACHINE FOR CARRYING OUT SUCH A METHOD - Google Patents

Description

Patent attorney <■ - - · ■ * ·. ·, ..... - .._.

Dipl .-! Ng. W. Jackisch .l \. ' .: ..: * .. \ / O / / C 1 O

Menzelstrasse 40, 7000 Stuttgart 1 - OH HD I OO

Fortuna-Werke · ο ■ _{A 38} i

Machine factory company

with limited liability I 7th Dec, 198 * 1

Pragstrasse 140

7000 Stuttgart 50

Method for determining the position of a workpiece in an NC-controlled machine and an NC-controlled machine for carrying out such a method

The invention relates to a method for determining the position of a workpiece in an NC-controlled machine according to the preamble of claim 1 and an NC-controlled machine for performing such a method according to the Preamble of claim 10.

When machining workpieces in NC-controlled machines, the workpieces must have a certain position in relation to the grinding wheel before and during the machining. Within a series, the workpieces to be machined have tolerances that must be taken into account when positioning. For this purpose, separate measuring devices are used , which are arranged on the machine and with which the position of the workpiece is determined. This measuring method is cumbersome and expensive, since the measuring device has to be realigned with respect to the workpieces. If, for example, two surfaces have to be measured on the workpiece, the measuring device must be brought into two different measuring positions. Such a method is therefore time-consuming and therefore costly. As a result, the performance of the NC-controlled machine cannot be fully utilized. In addition, it often causes problems to be able to accommodate the measuring device in the machine at all.

The invention is based on the object of equipping the generic method and the generic machine in such a way

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zubilden that the position determination can be carried out quickly and easily, and indeed in machines where there is only little space available for a measuring device.

In the method of the generic type, this object is achieved according to the invention with the characterizing features of claim 1 and solved in the generic machine according to the invention with the characterizing features of claim 10.

In the method according to the invention, the arithmetic unit of the NC-controlled machine is used to determine the position of the workpiece used. The position of the center point or the tailstock depends on the position of the workpiece in the machine. Therefore: the position of the workpiece with the arithmetic unit can be determined from the position of the tailstock by means of the measuring device be determined. In the arithmetic unit, from the signal supplied by the measuring device, the Position of the center point and thus of the workpiece can be determined.

The measuring device is in the machine according to the invention integrated so that no additional measuring device is required to determine the position. This allows when editing a series of workpieces the position determinations can be carried out very easily and quickly. Since the location of the Tailstock is detected with the measuring device, does not have to be in the area of the workpiece for a Measuring device or the like. Be provided so that the machine can be made compact.

Further features of the invention emerge from the further Claims, the description and the drawings.

The invention is illustrated by means of some in the drawings.

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- 7 presented exemplary embodiments explained in more detail. Show it

1 shows a schematic representation of a first embodiment of a machine according to the invention,

FIG. 2 shows, in a representation corresponding to FIG. 1, the machine in which a shorter workpiece is provided is,

3 shows a schematic representation of a second embodiment of a machine according to the invention with a workpiece whose face is to be machined,

4 shows the machine according to FIG. 3, in which a shorter workpiece is to be machined,

5 shows a schematic representation of a third embodiment of a machine according to the invention, with which a dimension f is determined as a reference for a length χ to be produced,

6 shows the machine according to FIG. 5, in which the workpiece after machining an end face 180 ° rotated is clamped again and made with a length χ on a workpiece shall be.

FIGS. 1 and 2 schematically show a machine which is NC-controlled. A workpiece 1 is clamped in the machine between two centering points 2 and 3. The center point 3 is part of a quill 4 which is housed ^{in a tailstock 4 1.} The quill 4 or another element that can be adjusted relative to the machine table has a measuring scale 5, by means of which the position of the centering tip 3 can be determined. To this end, a

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probe 6 provided '/ which is connected to the arithmetic unit 7 of the NC machine.

With the machine according to FIGS. 1 and 2, a workpiece type identification with respect to the workpiece length be performed. When the workpiece 1 is clamped between the centers 2, 3, the center point takes 3 a certain position with respect to the fixedly arranged scanning head 6. Using the measuring scale 5 can determine the position of the centering point 3 and enter it into the arithmetic unit 7. The position of the center point

2 is already programmed in the arithmetic unit 7, but it can also be communicated to the arithmetic unit 7 via a corresponding measuring device 5, 6. From the position of the centering point 2 and

3 the length of the workpiece 1 can be determined. If a shorter or longer workpiece 1 '(Fig. 2) clamped, then takes the center point 3 a different position. It is communicated to the arithmetic unit 7 via the scanning head 6. From this the length of the workpiece 1 'can again be seen. If the position of the center point 2 is not determined or not programmed, the workpiece type is recognized only the change in position of the center point 3 is used. Using the measuring system 5, 6, the length of the Determine the workpieces to be processed and thus carry out a workpiece type recognition. Since the scanning head 6 is connected to the arithmetic unit 7 of the NC machine, the measurement can be carried out even with limited space perform accurately without difficulty. In particular, no separate measuring device is required, which is attached to the Machine would have to be attached and has a corresponding space requirement.

In the machine according to FIGS. 3 and 4, a second measuring system 8, 9 is provided, which also consists of a measuring scale 8 and one connected to the arithmetic unit 7a

Scanning head 9 consists. The measuring scale 8 is on a machine table 10 is provided on which the centering tip 2 is mounted. The workpiece 1a between the two Centering points 2 and 3 is clamped, has an axial, narrow projection 11. The workpiece 1a is on its end face 12 processed, in the exemplary embodiment with a profile grinding wheel 13. So that the required amount can be ground away at the end face 12, it is necessary to use the To know the position of the end face 12. After clamping the workpiece 1a between the two centering points 2 and 3, the end face 12 of the workpiece 1a to be machined has a safety distance 14 from the profile grinding wheel 13. The machine table 10 together with the tailstock 4 * is now so far against it at creep speed the profile grinding wheel 13 moved until the end face 12 comes to rest on the profile grinding wheel. In this stop position, the scanning heads and 9 the arithmetic unit 7a of the NC machine reported the positions of the center point 3 and the machine table 10 and saved. If the same workpieces are then processed on the device, you can use the stored safety distance 14 and the stored stop position of the workpiece on the profile grinding wheel automatically moves the workpiece to be processed in the shortest possible time to its processing position will.

In Fig. 4, a workpiece 1a ^{1 is} shown, which is shorter than the workpiece 1a according to FIG. Since the work

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piece 1a ^{1 is} shorter, the machine table 10- and the centering point 3, if die.Meßeinrichtung 5,6 'and 8, 9 were not available, would have to be moved at slow speed up to the stop on the profile grinding wheel 13. As a result of the shorter length of the workpiece 1a ^1, this delivery path is longer than in the case of the longer workpiece 1a according to FIG

Machine could not work with great power. In the exemplary embodiment, however, as a result of the measuring devices 5, 6 and 8, 9, the delivery path and thus the delivery time are considerably shortened and, accordingly, the performance of the machine is significantly increased. On the basis of the measured values supplied by the two scanning heads 6 and 9, the length of the clamped workpiece 1a ¹ can be determined immediately. Since the length of the previously machined workpiece 1a has been stored in the arithmetic unit 7a, it is easy to determine by how much the workpiece 1a ^{1 is} shorter than the workpiece 1a by comparing the two workpiece lengths determined. Since the workpiece ^{1 a 1 is} also to be processed with the profile grinding wheel 13 on its end face 12 ', it must be brought up to the grinding wheel. Since the length of the workpiece 1a ^{1 is} determined with the arithmetic unit 7a and the safety distance 14 to the profile grinding disk has been stored in the arithmetic unit 7a, it can be used to determine how far the workpiece 1a ^{1 has} to be advanced up to the safety distance 14 against the profile disk 13 . Thus, controlled by the arithmetic unit 7a, the machine table 10 can be advanced against the profile grinding wheel 13 in rapid traverse until the end face 12 ″ has the safety distance 14 from the profile grinding wheel 13. In FIG 12 'at a safe distance

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14 from the profile grinding wheel 13 is switched to creep speed so that the workpiece 1a ^{1 is} slowly brought up to the profile grinding wheel.

With the machine according to FIGS. 3 and 4, the length of ^{the workpiece is already taken into account when positioning the workpiece 1a 1.} As a result, shorter workpieces 1a ¹ do not have to be fed over the entire distance from the profile grinding wheel 13 at creep speed, but with the help of the arithmetic unit 7a the shorter workpiece can first be brought up to the safety distance 14 to the profile grinding wheel in rapid traverse. Only then is it switched to creep speed. Regardless of whether a long or a short workpiece is clamped in the machine, the workpiece is only fed to the profile grinding wheel 13 at creep speed over the length of the safety distance 14. As a result, the setting times for the positioning of the workpieces are considerably reduced compared to the known machines and thus the performance of the machine. significantly increased. In addition, the safety distance 14 can be kept very small as a result of the described automatic control, whereby the delivery time is further reduced.

Of course, longer workpieces than the workpiece 1a according to FIG. 3 can also be clamped in the machine will. Here, too, it is automatically determined by means of the two measuring devices 5, 6 and 8, 9 by how much this workpiece is longer. Depending on the distance between the end face to be machined, this longer workpiece will it is then automatically positioned at the safety distance 14, controlled by the arithmetic unit.

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With the machine according to FIGS. 5 and 6, it is possible to automatically produce a length χ required on the workpiece 1b to manufacture precisely. With this machine it is possible to have opposing axial positions on the workpiece 1b to be recorded without a separate

To have to use positioning device. In practice, workpieces of the same series to be ground have different center depths. Depending on the workpiece, the center point 3 thus assumes a different position with the same machine setting. The quill 4 or another suitable machine element in turn carries the measuring scale 5 to which the scanning head 6 is assigned. The machine table 10 is provided with the measuring scale 8 for the scanning head 9. The workpiece 1b is in turn clamped between the two centrepoints 2 and 3, which each engage in a recess 16 and 17 in the end faces of end sections 18 and 19 of the workpiece with reduced diameter. The workpiece 1b is moved up to the grinding wheel 13 in the manner described and the end face 12b is ground off. A machine-related zero point M _{Q is} stored in the arithmetic unit 7b. After the grinding process has ended, the distance Z _{1 of} the grinding wheel 13 from the zero point. · Μ * is stored. The position of the center point 3 and thus the distance w of the point 20 of the center point 3 from the machine- _{related zero point M Q} can be determined with the help of the measuring device 5, 6 from the position of the center point 3. This determined value w is also entered into the arithmetic unit 7b. The distance f of the tip 20 from the finished end face 12b of the workpiece 1b can be determined from the two values Z ₁ and w according to the relationship f = Z _{1 - w.}

Then the workpiece 1b machined on an end face 12b is turned through 180 ° and again between the two centers 2 and 3 clamped (Fig. 6). With the grinding wheel 13, the other end face 21 is now

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of the workpiece 1b abraded. This face must now be sanded down until the distance χ between the two end faces 12b and 21 is reached. The following relationship is used for this:

A = f + χ + Z ₂

A is a parameter stored in the arithmetic unit 7b, which results from the distance between the machine-related zero point M ₀ and the free end 22 of the centering point 2, f is "the distance between the machined end face 12b and the recess 17 in the end section 19 of the workpiece 1b. This value f was determined during the machining of the end face 12b and stored in the arithmetic unit 7b, χ is the required distance between the two end faces 12b and 21 of the workpiece 1b. Z2 is the respective distance between the machine-related zero point M »and the to machined face 21. During the machining of the face 21, the workpiece 1b is fed in accordance with the removal on its face with the machine table 10. This changes the value A. With the measuring device 8, the position of the machine table 10 and thus of the workpiece 1b determine and thus calculate the dimension A, using the above relationship, the value χ during the Schle if process can be continuously calculated and compared with the stored target value. When the actual value agrees with the target value, the grinding process is ended. The machined workpiece 1b then has the required collar width x. In the manner described, the workpieces of a series can be precisely manufactured with the required collar width χ without difficulty. Even if the workpieces in a series have larger tolerances, they can be manufactured in the manner described with the required accuracy.

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The measuring devices described for the various. Embodiments are each formed by a measuring scale and a scanning head. The readhead can be a Be a rotary pulse generator, while a linear scale, an incremental scale / an absolute scale and as a measuring scale like. can be. In order to be able to determine the contact between the respective workpiece and the tool, Sensors provided, such as body switch sensors, which emit a signal as soon as this contact takes place. This signal is then used to terminate the infeed movement used.

Instead of the starting position determined by the contact between the workpiece and the tool, a programmed position into which the workpiece to be machined is brought. then a chip is removed from the workpiece in this programmed position with the respective tool. After the chip removal, the machined side of the workpiece is used as a reference surface and the position of this processed reference surface is saved in the arithmetic unit. The measure f (Fig. 5 and 6) can thus either by reporting the Position of the reference surface can be determined by a sensor or by machining.

The NC machines described can be used for grinding or turning rotationally symmetrical workpieces.

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Claims (14)

Expectations 1.) Method for determining the position of a workpiece in an NC-controlled, ι a Zeatrierspitase and a Arithmetic unit having machine in which the workpiece is clamped and the position of at least one point of the workpiece is determined with at least one measuring device, characterized in that the position of the centering point (3) determined with the measuring device (5, 6) and this determined value as a signal to the arithmetic unit (7, 7a, 7b) is supplied. 2. The method of claim 1, wherein the workpiece during machining with an NC-controlled machine table Machine is adjusted, characterized in that the position of the machine table (10) is determined with a further measuring device (8, 9) and the determined value is fed as a signal to the arithmetic unit (7a, 7b). 3. The method according to claim 1 or 2, characterized in that the actual measured value of the measuring device (5, 6) is stored with a Setpoint is compared, and that the arithmetic unit (7a, 7b) a control signal for moving the Machine table (10) releases when the actual measured value differs from the setpoint. - 2 - 4. The method according to any one of claims 1 to 3, characterized in that with the machine-side measuring device (8, 9) during machining Distance fc) to a surface (21) of the workpiece to be machined (1b) is measured from a reference point (12b). 5. The method according to claim 4, characterized in that the reference point (12b) is a further surface on the workpiece (1b). 6. The method according to claim 4 or 5, characterized in that the further surface (12b) first processed and with the quill-side measuring device (5, 6) the distance (f) between it and a recess (17) in the workpiece (1b) is determined. 7. The method according to claim 6, characterized in that the distance (f) is compared with a target value during processing and when it is reached of the setpoint the machining process is aborted. 8. The method according to any one of claims 4 to 7, characterized in that the workpiece (1b) is turned after the machining of the further surface (12b), that with the machine-side measuring device (8, 9) during the machining of the surface (21) of the workpiece (1b) the distance (x) between it and the further surface (12b) is determined and compared with a target value is, and that a signal to terminate the machining process is generated as soon as the determined distance value (x) corresponds to the target value. 9. The method according to claim 8, characterized in that after turning the workpiece (1b) during machining, a distance (A) between a stored machine-related zero point (Mq) and the recess (17) in the workpiece (1b) measured and from it the distance (x) between the two surfaces (12b / 21) of the workpiece (1b) is calculated. 10. NC-controlled machine for performing the method according to one of claims 1 to 9, with a movable one Machine table on which at least one tailstock is mounted, which can be adjusted relative to the machine table, and with an arithmetic unit, characterized in that the machine has at least one ^{measuring device (5, 6) assigned to the tailstock (4 1} ) and connected to the arithmetic unit (7, 7a _r 7b). 11. Machine according to claim 10, characterized in that the measuring device consists of a measuring scale (5) and a scanning head (6) whose Output is connected to an input of the arithmetic unit (7, 7a, 7b). 12. Machine according to claim 10 or 11, characterized in that the machine has at least one further measuring device assigned to the machine table (10) (8, 9) which is connected to the arithmetic unit (7a, 7b). 13. Machine according to claim 12, characterized in that the further measuring device (8, 9) consists of a measuring scale (8) and a scanning head (9), the output of which is connected to an input of the arithmetic unit (7a, 7b). 14. Machine according to one of claims 10 to 13, characterized in that the measuring device (5, 6) on the Tailstock quill (4) is arranged.